Tuesday, March 9, 2010

Columbia Fish Passage and Low Snowpack

With poor snowpack and minimal runoff looming this spring, dam and fishery managers in the Columbia Basin have been weighing the potential costs and benefits of various fish passage strategies. Over the last 8-10 years increased spill over hydroelectric dams has helped speed the passage of smolts out of the Columbia system, while other smolts have been collected and barged downriver in an attempt to reduce in river mortality. This year, with minimal snowpack available for spill some have been advocating for a fish passage strategy based largely on barging. Unfortunately barging is not without unintended consequences. Barged fish may survive passage down the Columbia at a higher rate, but the jury is still out as to the effectiveness of barging in the longer term. Barged fish are known to stray at a substantially higher rate. Straying is problematic because upriver stocks may loose a large number of potential spawners to lower river systems, and high stray rates can erode local adaptation.

With climate change predicted to further reduce snowpack in Columbia, future fish passage through the Snake system will pose a variety of problems. Low snowpack also means warmer temperatures for migrating adults during summer and fall, and a potential for increased prespawn mortality. This year is an example of what we can likely expect as the norm 20-30 years down the road and highlights the need to remove the four lower Snake River dams. Current measures are merely bandaids applied to a hemorrhaging patient that is the Snake system. With dam removal, the wild salmon and steelhead of the Snake River have a high liklihood of recovering substantially, without, wild stocks will continue to decline towards extinction.

see an article in the Columbia Basin Bulletin for fish passage plans in 2010:

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